Method of neutralizing a petroleum oil



Patented Dec. 18, "1934' UNITED STATE amnion or v mam osra'raoilsuu.

he: inseam, Wood mm, 111., Mda StandardtOil Company ration of'lndiana Chica o. a eorno No-Drawing. Application June 5, may sci-m No. 542,463

My invention relates to an oil refining process and it pertains more particularly to the neutral? ization and removal of naphtbenic' acids and similar impurities from lubricating oils.

In refining petroleum oils, particularly lubricating oils, it is necessary to treat them with sulfuric acid for the removal of asphaltic bodies and other impm'ities. Oils containing naphthenic acids must be treated for the removal of these emulsion-forming substances. Also,-oils which have been treated with sulfuric acid are apt to contain oil soluble sulfo acids difllcult to remove. When these oils are neutralized by the addition of aqueous alkaline solutions or by .the addition of oil to. concentrated aqueous alkaline solutions, water-in-oil emulsions are formed. .These emulsions are extremely diflicult to handle and hard to break. Water-soluble petroleum sulfonic acids or salts may be used for breaking these emulsions, but this treatment is often so severe that it is detrimental to the color of the finished oil. These water-in-oil emulsions not only present mechanical diili- -cultiesand cause thelloss of oil, but they prevent the complete removal of the naphthenic acids, which then interfere with subsequent refining of theoil, such'as percolation through iullers earth.

The object of my invention is to provide an improved method of neutralizing the petroleum oils,'particu1arly those containing 'naphthenic acids, to avoid water-in-oil emulsions, to obtain stable oils with stable color, to decrease the cost of treating reagents, and tosimplify the process generally. A further object is to avoid oil losses which were heretofore causedby the formation of dimcultly controllable water-in-oil emulsions formed by neutralization after acid treatment. -A further obiectis to providean improved method of removing naphthenic compounds from petroleum oils. Other objects-will be apparent from the following detailed description. y

In practicing my invention I'introduce sour acid-treated oil or oil. containing naphthenic acids into 'a ,dflute aqueous alkaline solution under conditions which will'insure the formation of an oil-in-wateremulsion. The oil droplets are so small that'they present a large surface area for contact with the alkaline reagent and most of the naphthenic soaps pass into the aqueous phase. Oil-in-wateremulsions are easilybroken and after stratification the neutralizedoilmaybecontactedwithclayand finished to yield a'stabl'e oilof excellent color.

I- have found that by arefully regulating reaction conditions an oil-in-water emulsion'can be produced in a neutralizing step instead of a water-in-oil emulsion. To produce'an oil-inwater emulsion I add the-oil to an aqueous 6 alkaline solution, the concentration: of which is notv greater than about 10 The optimum temperature conditions will vary with the viscosity of the oil undergoingtreatment and it will fall, generally,-within the range of about 10 F. to F. when the aqueous alkaline neutralizing solution contains under 1% of sodium hydroxide (or the equivalent of other alkaline reagents); I may break the oil-in-water emulsion by the addition'of electrolyteasuch as is calcium chloride, sodium chloride. aluminum chloride or other reagent which normally would tend to form a water-in-oil emulsion. When the addition of an electrolyte or other reagent is objectionable because of its contamination of 20 the naphthenic' soaps produced, cost, or other reason, and when it is desired to avoid the introduction of emulsion breakers, I may use an aqueous neutralizing'solution-containing 1 to 10% of sodium hydroxide or an equivalent 5 amount of other'alkali. The use of these dilute alkaline solutions for the neutralization of oil is a markeddeparture from conventional practice but I have found that it is remarkably eifective and that it offers many advantages.

My invention will be more clearly understood from'the description of its application to certain oils. As an example, I may treat a. Winkler lubricating oil (having a Saybolt viscosity of 1.15 at 21051 with 89% to 93% siumric acid, 35 using aboutone pound of acid per gallon of oil. This treating is preferably efiected by agitation with air at a temperature of about lo-120 F. and for a period of'about one-half hour. After this treatment the oil is allowed to settle and it 5 i is removed from the sludge by decantation. Instead-of neutralizing this sour oil by adding concentrated caustic thereto, I introduce the oil- 'ture of about -18051. Separation of the phases occin's quickly, but it several hours for theioil layer to'become clear. The

clear oil is decanted and washed with water to remove any soaps or caustic which might have been dissolved or suspended in the oil. The resuiting oil may have an organic acidity of about .04-.08 mg. of KOH per gram and a color of about 4 to 4 N. P. A. This oil is then contacted with fullers earth, such as Olmstead clay, using about 4- pound per gallon of oil and heating the mixture to about 300 F. Because of the low acidity, the oil is easily filtered, and higher yields are obtained than with oils washed by the former processes using soaps.

As another example of my invention I may,

the oil with an equal volume of an aqueous .5%

sodium hydroxide solution. Both the oil and the caustic are preferably at a temperature of about 85 F. and when the oil is poured slowly with agitation into the sodium hydroxide solution an immediate emulsion of the oil-in-water type is formed. The emulsion may be agitated for about two minutes with air, after which a small amount of 10% CaClz solution is added to break the emulsion. The batch is then allowed to settle. I prefer to heat the batch to about 150 F. to expedite settling and I find that a good separation of phases occurs immediately but that two or. three hours are required for the oil layer to become clear. After the clear oil layer is decanted and washed with water it may have an acidity of .07 mg. of KOH per gram. This oil may then be contacted with fuller's earth, such as Olmstead clear. at about 300 F. using about pound of clay per gallonof oil, and after this treatment the oil may be .readily filtered. The finished oil may have an organic acidity of about .05 mg. of KOH per gram and a color of 135-2 N. P. A.

In the above examples I have formed oil-inwater emulsions and have broken-the emulsions in one case by using CaCh solution and in the other by merely heating and letting it stand. When concentrations of caustic less than 1% are used I find that the emulsion is more stable and, in such cases, I break the emulsion by the addition of an electrolyte solution such as a 10% calcium chloride solution. .It is important that the concentration of,the neutralizing solution bebelow 10% because more concentrated solutions tend to form water-in-oil emulsions which are hard to treat and hard to break. By using caustic soda solutions above. 1% I find that unstable oil-in-water emulsions are formed. It

is only when the concentrations are below 1%.

that the electrolytes or other emulsion breakers are required.

An important feature of my invention .is the removal of naphthenic compounds to such an extent that the clay may be filtered from the contacted oil much more readily,. whereby I may be easily broken by the addition of an elec-. trolyte, such as calcium chloride. Furthermore, the napthenic soaps formed when the oil is introduced into the aqueous solution causes the emulsification of the oil in very fine or small droplets, most of the soap being present in the aqueous phase. Due to this fine dispersion of the oil particles, intimate contact is obtained between oil and aqueous phase so that the neutralization reaction proceeds very rapidly. As the neutralization proceeds the soap is trans,- ferred to the film surrounding the oil particle, and since this film is in equilibrium with the soap in solution, a largeamount of the soap is transferred from the oil to the aqueous solution. When the'emulsion is broken, the oil is substantially'free from naphthenic acids and the naphthenic soaps can be recovered from the aqueous phase by .known methods of acidification and distillation. r

While I have stated that excellent results are obtained by using equal volumes of oil and water, it is understood that I do not limit myself to this detail or to any other detail except as defined by the appended claims which should be given as broad an interpretation as the prior art will permit. The aqueous neutralizing reagent should be dilute and should preferably contain only about 1.0-3.0% caustic (or an equivalent amount of other neutralizing reagent). The sodium hydroxide present in the aqueous phase should preferably be 50% more than that necessary to neutralize the acidity .of

the oil.

It is understood that heavy distillates may be diluted with naphtha prior to this treatment and that other expedients may be used in accordance with conventional refinery practice.

1. .The method of neutralizing a petroleum oil containing emulsion-forming oil soluble organic acids, which comprises adding said oil toa large volume of dilute aqueous alkaline solution with agitation under conditions which will insur'e the formation of an oil-in-water emulsion, and subsequently breaking the emulsion into an oil phase and a water phase.

2. The method of claim 1 wherein the concentration of the aqueous alkaline solution is less than 10%. w

3. The method of claiml wherein the concentration of the aqueous alkaline solution is from 1 to 3%.

4. The method of neutralizing acid bearing vis-.

cous petroleum oil which comprises adding it to a large volume of a dilute aqueous alkaline solution with-agitation under conditions which will insure the formation of an oil-in-water emulsion, breaking said emulsion and separating said oil from said solution, and contacting said oil with fullers earth at about 300 F.

5. The method of refining a viscous petroleum oil which comprises treating it with sulfuric acid, neutralizing the resulting acid bearing. oil by pouring it into a large volume of a dilute aqueous alkaline solution under conditions which will insure the formation of an oil-in-water emulsion, breaking said emulsion, separating the oil from the aqueous phase, contacting said oil with fullers earth at about 300 F., and filtering said hot oil to removethe fuller's earth therefrom.

6. The method of refining a viscous petroleum oil which comprises treating it-with concentrated sulfuric acid, adding the resulting acid-bear- 9. The method of claim 7 wherein calcium ing oil to a substantially equal volume of a dilute aqueous alkaline solution with agitation under conditions which will insure the formation oi an oil-in-water emulsion, heating said emulsion to separate the oil from the aqueous phase, contacting the oil with clay at an elevated temperature. and removing said clay from said 011 by filtration.

'7. The method of removing naphthenic acidsoil-in-water emulsifier, adding further amounts of oil under conditions which will insure the formation of a finely dispersed emulsion whereby rapid-neutralization is eflected and naphthenic soaps are transferred to the aqueous phase, and

chloride is added for breaking the emulsion.

10. The method of neutralizing an acid-bearing petroleum oil which comprises adding said oil to a substantially equal volume oi. an aqueous solution containing about one and one-half times the amount of alkali base required for the complete neutralization of said oil, and agitating the mixture to form an oil-in-water emulsion.

'11. The method of separating uncontaminated oil-soluble naphthenic acids from mineral oils which comprises adding the oil gradually with agitation to a large volume of a solution of aqueous alkali having a strength of not more than 3%, allowing the resulting emulsion to stand until separated into layers, separating the aqueous layer from the oil layer and acidifying the aqueous layer to recover the naphthenic acids therefrom.

' JACK ROBINSQN. 

